I have an hei system. 71 olds cutlass supreme. i bought this tach without any wiring diagram. Any information would be helpful.

 

Typically power, ground, tach signal and light.

Tach signal connects to the TACH terminal on the distributor.
Power and Ground should be self explanatory. You can typically find a switched power connection on the fuse box, such as the IGN terminal.
Light ties into your dash light wiring.

So you need to determine which of those spade terminals ais power and which is the tach input.

 

So far i have the light wire to grey light wire from clock. i have the ground wire. the last two male terminals are what i need to know where pwr and tach wires plug up.

 

I have a Mallory set up which i can't find a terminal for a tach. Diagram reads tie tach wire (green if I remember correctly )to the neg side of the coil. Mine has a terminal block from neg coil mounted on the firewall which makes it easier. Will dig up and post that diagram. Going from memory Dash light/white tach wire, ground/blk tach wire, ignition/red tach wire, neg coil/ green tach wire

 

Whats the worst that can happen if I incorrectly hook up tach and power wires?

 

The smoke gets out. Smoke is what makes it work. Typically green is the tach signal wire, black is ground, red is power, and blue (or grey) is light.

 

Perhaps contact the manufacturer? There aren't too many sources for that aftermarket Olds tach. The problem is that the ground and light terminals are obvious, but the two spade terminals are unlabeled. On will connect to power and one to the "-" terminal of the coil (or the TACH terminal of an HEI), but you don't know which is which.

 

Looks like the tach that GM Sports Salvage sells. I would give them a call.

http://www.gmsports.com/content/1968...***-tachometer

 

^^^this once the magic smoke has been released electronics never work again w out replacement parts.....

 

I'm sure you know that it is being repro'd now... at least for cars on your side of the pond.

 

Talked with GM Sports. They directed me to the guy who makes the tachs. He walked me through the install.